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E. coli
0157
Cooking Recommendations
for Tenderized Beef, Minute
Steaks and Burgers
An Initiative of the E. coli O157 Research and Education Strategy
Research and
Education
Strategy
Contents
P2
Mechanically
Tenderized Steaks
P3
Mechanically
Tenderized
Roast Beef
About the E. coli O157 Research
and Education Strategy
The E.coli O157 Research and Education Strategy was developed in consultation with
Canadian beef processors to address the key food safety issues arising from the 2012
recall with a view to prevent a future reoccurrence. A major focus of the Strategy was
in relation to the food safety of the so called “non-intact” product category where
bacteria may be transferred into the centre of the beef product during processing.
Ultimately, research conducted under the Strategy contributed to the scientific rationale
for new labels for tenderized beef across Canada. The pages that follow summarize
the key findings for mechanically tenderized beef steaks and roasts, as well as minute
steaks and burgers.
The research carried out under the Strategy was made possible by financial support
from the Alberta Livestock and Meat Agency, the Beef Cattle Research Council and the
National Beef Check-off.
In Memoriam
Dr. Gill was employed by the Meat Research Institute of
New Zealand in his early career before he was recruited
in 1990 by Agriculture and Agri-Food Canada (AAFC). He
worked as a senior research scientist in the field of meat
microbiology at the AAFC Research and Development
Centre in Lacombe, Alberta for 25 years until his death in
December 2014.
P4
Minute
Steaks
Dr. Colin Gill
1943 - 2014
P5
Cleaning
Tenderizing
Equipment
P6
Beef Burgers
Dr. Gill believed in the importance of practically oriented
research and he spent a great deal of time in packing
plants and other commercial facilities in Canada to assess
and enhance production practices. Among Dr. Gill’s many
achievements was his contribution to the design and
implementation of the carcass pasteurizer for which he
was granted three patents.
Just as important as his scientific ability was his passion for
the work he conducted. He was 71 at the time of his death and never once declined
to take on a new project related to beef safety. Some of his most important work was
conducted in his last five years including the mentoring of Dr. Xianqin Yang who is now
carrying on his research at the AAFC Lacombe Research and Development Centre in
Lacombe. Dr. Gill produced approximately 250 scientific manuscripts that have been
cited more than 3,000 times in publications by scientists around the world.
Dr. Gill was an essential contributor to the research conducted under the E. coli O157
Research and Education Strategy and his contribution is gratefully acknowledged by the
Canadian Cattlemen’s Association.
Mechanically Tenderized Steak
Beef Quality and Mechanical Tenderization
Beef tenderness has been shown to be a major contributor
to consumer satisfaction. Tenderness in beef is determined
by the amount and type of connective tissue and muscle
fibres. Tenderness can be improved by aging as well as
by cooking methods, such as the use of moist heat over
extended periods, which can soften connective tissue. The
overall tenderness of meat can also be improved by cutting
through muscle fibres and connective tissue using blades
or needles. Mechanical tenderization can enhance eating
quality, especially beef made from parts of the animal used
in locomotion which are naturally tougher. Tenderness is
enhanced without changes to the nutritional value of beef.
About Mechanically Tenderized Beef
Mechanical tenderization has been used by the Canadian
beef industry for many years at retail stores, meat processors
and in the restaurant sector. Mechanical tenderization can
also occur at home, as tenderizing tools intended for
consumer use are available. Regardless of where it is used,
mechanical tenderization is typically performed by passing
blades or needles through meat products. Often this
tenderizing treatment does not produce visible changes to
the product.
Steak A was turned over every four minutes while cooking to a
63°C internal temperature. Steak B was turned every 60 seconds
while cooking to the same 63°C internal temperature. Doneness
level in steak B is more even throughout the steak.
Conclusions
Research on Tenderized Steaks
Due to the potential for bacteria on the exterior of beef to
be transferred to the centre of the product it is important
that mechanically tenderized beef products are not cooked
to less than medium-rare (63°C or 145°F). In the case of
steaks, research performed at the AAFC Lacombe Research
and Development Centre indicated that the edges of a steak
may at times be cooler than the centre. If a steak is turned
over only once the temperature reached throughout the
steak can be inconsistent. By turning over the steak at least
twice when cooking to 63°C, the temperature will be more
even which is helpful from both a food safety and an eating
quality perspective.
Mechanically tenderized beef steaks and roasts are now
required by Health Canada to be labelled so they can be
recognized by consumers. These labels also include cooking
instructions which indicate that tenderized beef should be
cooked to a minimum internal temperature of 63°C for both
steaks and roasts. This temperature corresponds to a
medium-rare doneness level. An additional instruction is
provided for steaks that recommends to turn the steak over
at least twice during cooking. These procedures are easy to
follow and already utilized by the majority of Canadians for
cooking untenderized beef products.
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Mechanically Tenderized Roasts
How Canadian Consumers Cook Beef Roasts
A survey of Canadian consumers commissioned by the
Canadian Cattlemen’s Association showed that the majority
of Canadian consumers prefer to cook their roasts in ovens
(77%) or slow cookers/crock pots (54%).1 Roasts of small
sizes (2 kg or less) are preferred by more than 80% of the
respondents. Oven temperatures in the range of 160 to
180°C are used by about 50% of Canadian consumers.
More than 90% of Canadian consumers cook their roasts to
internal temperatures of 63°C or higher.
Research on Mechanically Tenderized Roasts
Laboratory research was performed at the AAFC Lacombe
Research and Development Centre to determine the
minimum internal roast temperature at which a very high
level of E. coli O157:H7 could be inactivated. E. coli O157:H7
bacteria were injected into the roasts at various points
to simulate mechanical tenderization. Approximately 10
million E. coli O157:H7 bacteria were placed into eye of
round roasts and prime rib roasts of 0.6 to 2.1 kg in weight.
Such high levels of E. coli bacteria would not be found in
reality, however they are utilized to test cooking methods of
tenderized beef in the laboratory.
The roasts were cooked in conventional or convection toaster
ovens operated at various temperatures. The slow cooker
was tested at the high or low heat settings. The reduction in
numbers of E. coli O157:H7 at each location in the meat as a
result of cooking was determined.
Slow Cookers and Tenderized Roasts
After innoculation E. coli O157:H7, roasts were cooked to
60°C or 63°C (medium rare) internal temperature in the
slow cooker at either low or high setting. No surviving E.
coli O157 could be found when roasts were cooked to 63°C
at either high or low settings although not all E. coli were
destroyed at the 60°C internal roast temperature.
Convection Ovens and Tenderized Roasts
Eye of round roasts were cooked to 65, 60, or 63°C at the
centre of the roast in a convection oven operated at 120,
140, 180, and 200°C.
At the lowest oven temperature of 120°C it was necessary to
cook roasts to 65°C at
the centre to destroy
the high level of E.
coli used. While not
all E. coli were killed
at 63°C the reduction
is likely sufficient to
ensure product safety
as very high levels of
bacteria were used in
the experiment.
When the oven was
operated at 140 or 180°C all E. coli were killed even at 60°C
internal roast temperature. At 200°C oven temperature all E.
coli were killed at 63°C with some bacteria survival at 60°C.
Conventional Ovens and Tenderized Roasts
When conventional ovens were operated at 120°C all of the
bacteria were killed at 63°C internal temperature. At 60°C
there was limited surviving bacteria even with the very high
numbers used in the laboratory experiment. However, when
the oven was operated at 210°C it was necessary to cook
the product to 71°C.
Conclusions
Both the temperature at which the oven is operated and
the internal temperature of the beef roast following cooking
are important to food safety. It is recommended that
mechanically tenderized roasts be cooked at 140 to 180°C
oven temperature to a product temperature of 63°C. At
oven temperatures higher than 180°C with small roasts it
would be advisable to cook mechanically tenderized roasts to
higher temperatures.
1. National survey of 1,000 Canadian consumers commissioned by the Canadian Cattlemen’s Association and conducted by an independent market research firm.
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Minute Steaks
About Beef Minute
(Cubed) Steaks
One of the popular ways of
mechanically tenderizing meat is
cubing in which a machine with
two sets of pointed discs cut
muscle fibers from boneless cuts
without tearing them (Figure 1).
Cubing can also be done manually using a butcher’s mallet.
In the cubing process, irregular pieces of meat can also be
“knitted” together to form a more attractive cut. Cubed
steak is also called a minute steak because it can be cooked
quickly.
to 63°C and flipped twice there was not always an
adequate reduction of E. coli O157. When minutes steaks
were turned three times and cooked for a total of eight
minutes or were turned four times and cooked for six
minutes, E. coli O157:H7 throughout the steaks was
eliminated. The average final temperatures reached under
these conditions was 72 and 67°C, respectively.
Conclusions
One cooking method to ensure the safety of minute steaks
is to turn them over twice during cooking to 71°C. The
majority of Canadians already prepare minute steaks in this
manner.
Canadian Minute Steak Cooking Practices
A survey of Canadian consumers showed that the majority
prefer to cook their minute steaks by pan frying (63%) and
to a degree of doneness of medium (71°C) or higher (68%).
The vast majority of consumers (96%) flip their minute steaks
once or more during cooking.1
A
Research on Minute Steaks
Laboratory research was performed at the AAFC Lacombe
Research and Development Centre. Approximately 10 million
E. coli O157:H7 were injected at multiple locations into
minute steaks of approximately 125 grams in weight. Such
high levels of E. coli bacteria would not be found in reality,
however they are utilized to test cooking methods of minute
steaks in the laboratory.
B
The inoculated minute steaks were cooked on a hot plate
operated at 200°C, to simulate medium to high heat pan
frying. Various cooking times and flipping frequencies were
examined along with several end-point internal temperatures.
When minute steaks were turned over twice during cooking
to a final temperature of 71°C at the thickest point of the
meat, it was possible to destroy one million or more E. coli
O157. This type of reduction is considered by Health Canada
to ensure food safety. When minute steaks were cooked
Fig. 1 Mechanical tenderizer (A) and its mechanisms (B) used
for making minute steaks.
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Cleaning Tenderizing Equipment
Cleaning Meat Tenderizing Equipment
There are two objectives when cleaning meat tenderizing
equipment. These are the removal of food particles and
residues to obtain visibly clean equipment, and sanitizing to
reduce numbers of bacteria on the equipment to acceptable
levels. Tenderizing equipment can be more challenging to
clean because of the presence of numerous thin blades or
needles. If the equipment is not adequately cleaned and
sanitized it is possible that bacteria will be transferred to
meat that is passed through the equipment during
tenderizing operations.
Research on Cleaning Procedures
The procedures used in a commercial operation for cleaning
mechanical tenderizers and their effectiveness were studied.
Microbiological samples were taken from the tenderizing
equipment (Ross Industrial model TC700) before cleaning,
immediately after cleaning and also before use on the
morning of the next day.
Following cleaning at the commercial operation it was
found that the number of bacteria on equipment varied
by a factor of 10 from day-to-day. Further, the numbers of
bacteria on the equipment after use was similar to levels
found on the cleaned equipment just before use the next
morning. This indicates that while the equipment appeared
visibly clean, bacterial contamination remained. However,
in most instances the bacteria that remained after cleaning
were of the types more likely to contribute to spoilage than
foodborne illness.
The results of the microbiological testing were shared with
cleaning personnel and several aspects of the cleaning
methods were studied in the laboratory. Laboratory testing
found that washing equipment with warm (55°C) water
was very similar in effectiveness as hot (90°C) water. While
hot water would be expected to help inactivate bacteria,
it can also alter the detergent properties of cleaning
agents and result in films of denatured protein to form on
the equipment. It was also found that drying equipment
following cleaning helped prevent growth of bacteria
overnight. Drying may be particularly helpful to some
facilities that are not able to store cleaned equipment at
refrigeration temperatures until use the next morning.
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Examples of commonly used tenderizing equipment in
commercial use.
Microbiological testing of the equipment at the commercial
facility was then conducted following cleaning with the
revised procedures and holding of the cleaned equipment
in a cooler until use the next morning. The findings showed
more than a 90% improvement in the total number of
bacteria on the equipment with the modified cleaning
methods and storing equipment in a refrigerated area
overnight.
Conclusions
While the risk of hazardous bacterial contamination of
tenderizing equipment would seem to be small, appropriate
cleaning as well as drying and ideally refrigeration of
tenderizing equipment is necessary if such risks are to be
fully addressed. In small operations where microbiological
testing is infrequent or not an option, it is especially
important that cleaning and sanitation procedures are
well developed. The objective of removing and controlling
bacterial contaminants as well as visible residue on
equipment should be well understood by cleaning personnel.
Beef Burgers
How Canadians Cook Burgers
A survey of Canadian consumers commissioned by the
Canadian Cattlemen’s Association showed that 51%
of Canadian consumers prefer to cook their burgers by
barbecue grill (51%) and to a degree of doneness of
medium (71°C) or higher (90%). Most consumers (75%)
turn their burgers twice or more frequently during cooking.1
Research on Beef Burgers
Laboratory research was performed at the AAFC Lacombe
Research and Development Centre. Approximately 10
million E. coli O157:H7 were injected at the centre and
edges of burgers of approximately 120 grams in weight.
Such high levels of E. coli bacteria would not be found in
reality, however they are utilized to test cooking methods
for hamburger in the laboratory. Health Canada requires
that cooking methods be demonstrated to be capable of
eliminating large numbers of E. coli O157:H7 e.g. 100,000
bacteria reduced to zero.
Burgers were cooked from frozen or chilled state using
an electric barbecue. Burgers were cooked to 67 or 71°C
internal temperature with flipping of the burger one to three
times. During cooking to 71°C, the burgers were flipped
once at six minutes, or twice at three and six minutes for
chilled or four and eight minutes for frozen.
When burgers were flipped once during cooking to 71°C,
the elimination of E. coli O157:H7 was not complete, and
higher levels remained in burgers cooked from frozen.
However, when burgers were flipped twice during cooking
to 71°C, E. coli O157:H7 was eliminated throughout the
burgers irrespective of whether or not the burgers were
frozen.
Given the effectiveness of flipping burgers twice, burgers
were also cooked to 67°C to determine if lower burger endpoint temperatures were safe. However, neither flipping
once, twice or three times was sufficient to ensure product
safety.
Conclusions
The recommended method for cooking burgers is to achieve
an internal temperature of 71°C with flipping at least twice
during cooking. This recommendation is consistent with the
current practices of the majority of Canadian consumers.
1. National survey of 1,000 Canadian consumers commissioned by the Canadian
Cattlemen’s Association and conducted by an independent market research firm.
The average time it took to cook frozen burgers to the same
final temperature with the same turning frequency was more
than three minutes longer than that for chilled burgers.
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Cooking Recommendations
for Tenderized Beef, Minute
Steaks and Burgers
An Initiative of the E. coli O157 Research and Education Strategy
Industry Commentary
“The E. coli O157 Research and Education Strategy represents a partnership
between Canada’s cattle production and beef processing sectors to identify
priority areas for beef safety research. The work that has been undertaken as
part of the Strategy has provided the scientific foundation for new labelling
approaches for mechanically tenderized beef. It also provides important
perspectives on how Canadians prefer to prepare beef products which can
help guide industry communication and future research initiatives. “
Dennis Laycraft
Executive Vice President, Canadian Cattlemen’s Association
“The mechanical tenderization of steaks and roasts continues to serve as
an important intervention for the Canadian industry to enhance beef
tenderness, particularly for cuts from the round and chuck. The work
conducted under the E. coli O157 Research and Education Strategy
provides recommendations for cooking these products which are both
science-based and practical. “
Andrea Brocklebank
Executive Director, Beef Cattle Research Council
“Robust food safety processes and systems are essential to maintaining
the sustainability of Canada’s agriculture industry. Research, like that
conducted through the E. coli O157 Research and Education Strategy,
demonstrates Canada’s meat and livestock industry is committed to
producing, processing and retailing safe and superior foods for the
end user.”
Gordon Cove
President and CEO, Alberta Livestock and Meat Agency
The CCA is a non-profit federation comprised of eight provincial member cattle associations that
provide representation to a national, producer-led board of directors. The CCA’s vision is to have
a dynamic, profitable Canadian beef industry with high-quality beef products recognized as the
most outstanding by customers at home and around the world.